Water tube boiler



June 18, F. AA EN WATER TUBE BOILER Filed July 27, 1952 4 Sheets-Sheet 1 0000000. w m G E 0 ,O o w W lllllll a 4 O o Y .O W O. 0 0 M w w .g 0 0 7 0 J m M O o 0 o O 0 w o Q m 0 O 0000000 v June 18, 1935 F GRAAFEN WATER TUBE BOILER Filed July 2'7, 1932 4 Sheets-Sheet 2 ll1lllltnlllflfllllllf4rl Fly 4 June 18, 1935. F. GRAAFEN 2,005,543

WATER .TUBE BOILER Filed July 27, 1932 4 Sheets-Sheet 3 Fig. 5. &

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-oooooooooo oooooo wuaqoooo o o o o o o o o o o o o o o o o o 8 8 o o o o o o o o o o o o 0 8 r 8 8 g o a y'aahw Patented June 18, 1935 PATENT OFFICE Application July 27, 1932, Serial No. 624,948 In Germany August 30, 1929 Claims.

My invention relates to improvements in watertube boilers, the principal characteristic of which is a construction wherein water-tubes form the roof of, or partly or wholly enclose a furnace 5 chamber in the shape of an elongated flue, whereby a good mingling and combustion of the furnace gases as they travel over the fire and along the tubular furnace chamber are realized.

Good results are obtained by a boiler accord- IO ing to the present invention, in which only the roof of the tubular furnace chamber is formed by or lined with, water-tubes. Preferably, however, the roof and sides both are formed by, or

lined with, water-tubes extending in the longitudinal direction of the furnace.

The employment in water-tube boilers of furnace chambers construced as above described is of particular importance in combination with automatic stoker grates, or mechanical stokers in general.

Such grates frequently suffer from the drawback of unevenly distributed supplies of air at different portions of the grate, and more particularly the front portion of the grate receives an insufiicient supply of air Whilst the rear portion of the grate receives an excess supply of air.

Where the gases ascend directly from the grate between the water-tubes of inclined water-tube boilers, without the mingling of the furnace gases complete combustion is not achieved, since the comparatively cold gases and/ or those containing an excess of combustible gases and a deficiency of air above the grate, particularly over the front portion thereof, escape without such mingling with the burning or flaming gases from the grate and particularly those over the rear portion of the grate which contain hardly any combustible gases and excess of air, which would result in a more economical combustion.

This drawback is overcome by the tubular shape of the furnace chamber which is the subject of the present invention, because the furnace gases from diiferent portions of the grate are compelled to travel over the grate along the entire furnace chamber in a direction approximately parallel to the surface of the grate, and .in their travel the comparatively cold gases and/or those mixed with an insufficient amount of air, particularly from the front portion of the grate, are caused to 50 thoroughly mingle with the burning or flaming gases and those mixed with an excess of air, particularly from the rear portion of the grate whereby eflicient and, therefore, economical, combustion is produced.

Economical combustion is further promoted in accordance with the present invention by reason of .the tubular furnace chamber being extended beyond the end of the grate sloping downwards, whereby a whirling or eddying of the gases is produced which assists their being mingled together.

The further guiding of the hot gases can be effected in various ways.

Conveniently and advantageously, the gases may be led back either above or below the furnace chamber proper towards its front contrary to their previous direction of flow, as will be hereinafter more particularly described in detail.

In order that the present invention may be the more readily understood, reference is had to the various embodiments illustrated, by way of example, in the accompanying drawings, in which:-

Fig. 1 is a diagrammatic side elevation of a boiler in accordance with this invention.

Fig. 2 shows diagrammatically a section along the line 2-2 in Fig. 1.

.Fig 3 is a, diagrammatic side elevation of a modification of the boiler which is the subject of the present invention, the furnace being split up into cells.

' Fig. 4 is a diagrammatic cross section through Fig. 3 along line llll in Fig. 3.

Figs. 5 to 8 are vertical sections showing various methods of arranging water-tubes inside the tubular furnace chamber.

Fig. 9 shows in vertical section along the line il-ll in Fig. 3 an arrangement of deflectors.

Fig. 10 is a diagrammatic section perpendicular to Fig. 9 along line l2--I2 in Fig. 3.

Figs. 11 and 12 show in vertical section two further constructions of the roof of the furnace.

As shown in Figs. 1 and 2, the combustion or furnace chamber z is of elongated substantially tube shape and is formed of water tubes 0L and b. The tubes a form part of the grate, while the tubes 1) form the roof of the furnace chamber. Also the sides of the furnace chamber are preferably formed of water tubes, whereby all brickwork is completely dispensed with and the cost of construction and up-keep is considerably reduced. However, while I prefer to form both the roof and the sides of the furnace chamber of water tubes (19), good results are also obtained where only the roof is composed of water-tubes,

in which case the sides will be made of brick. As shown at the end or" the furnace chamber, the water tubes 2) are downwardly directed. In this manner, there occurs at the end of the grate an abrupt change in the direction of the flow of gases, which considerably promotes the mingling of the gases and their economical and complete combustion.

The water tubes a forming part of the grate are preferably connected directly to the boiler o as shown in Fig 1, these tubes being, therefore, used for conducting the boiler water back into the lower drum shown at u.

In the embodiment shown in Figs. 1 and 2, the furnace gases, directed downwards, pass through the spaced descending grate tubes 01., in a reverse direction to their previous direction of flow into the space y below the grate in which space a single or multiple superheater a can be housed. The flames being conducted in this way, the thorough admixture and burning of the furnace gases are greatly enhanced. This thorough mingling can be assisted by the installation in the rearward portion of the grate chamber or also in the up or down draught chamber of compressed air or steam mixing nozzles, or other means for mixing the gases, such as an. air propeller w inserted between small inspection slits, hereinafter described, in the row of tubes, the driving motor being mounted outside.

For a mixing propeller of this type at the rear end of the combustion chamber could, of course, also be substituted a fan-like, to-and-fro swinging mixing plate or, as already mentioned, noz-- zles. The result is that by the still more thorough mingling of the gases, a high carbon dioxide content of the flue gases is attained, as compared with water-tube boilers hitherto used, which have a great tendency to decompose and fractionate the furnace gases, and efficient i. e., economical combustion is insured by as much air as possible being mixed with the gases.

The grate can be of any desired type. Where a water-cooled grate is used, it can be connected to the boiler, as shown in Fig. 1. The movement of the layer of fuel on a grate of this type can be effected by any desired means, for example by means of reciprocated serrated feeders, cooled or non-cooled, and mounted between the watertubes or around the water-tubes. Any other desired means can, however, be employed for feeding the fuel. By the insertion of the water-cooled grate in the water-circulation circuit of the boiler, this circulation will thereby be considerably simplified.

The grate tubes a represent the return pipes for the water from the steam drum 0, which water is also fed, to the water or mud drum u. slanting drums can be employed, and the water-tubes can be connected to the drums either directly or with the aid of sectional tubes 3" and tubes 0. Of course, special return pipes can also be provided for the purpose of conveying the boiler Water from the upper drum to the lower drum, from whence it ascends again through the heated water-tubes.

Other devices can also be arranged in the space 'J in place of the superheater, or this space can be left entirely unoccupied and can then be used, as a return chamber. Moreover, it will be found advantageous to extend the bed of the grate somewhat behind the end of the furnace (say, .75 metre) so as to form at that point a dam for the incandescent fuel and, if need be, to assist combustion by the bridge-like effects so introduced. This rearward damming surface (1 arranged somewhat steeper (say 25) behind the end of the grate is so shaped in front of the spaced descending portions 0, c, 0 of the water-tubes that the clinkers and ashes must slide a certain distance over the rearward portions of the bent tubes before they are discharged through the spaced descending tubes into the ash pit. The bends c, c, c are so shaped that fragments of clinker cannot remain suspended there, whilst at the same time the formation of the dreaded nestlike deposits on the tubes is kept down by the fragments of clinker sliding down on the tubes.

In place of the damming surface d, the arrangement can also be such that the feed movement of the layer of fuel in the last part can be retarded by a suitable design of the grate.

Where the grate is not joined on to the boiler, but is cooled by means of a special cooling medium circulating system, the grate tubes need not, of course, be extended downwards and bent as, shown in Fig. 1. The grate can end, for example, at the end of the damming surface d. The same is the case where a non-cooled grate is used.

One great advantage of the improved boiler which is the subject of the present invention is that the transition of the heat into the watertube is effected almost exclusively by the absorption of radiant heat. It is, of course, most essential that the water-tubes shall be kept clean, more particularly where coal rich in gas is burnt, and free from incrustations of clinker or the like. While this end is self achieved by the new boiler, it can also be further assisted by special means. The flames shoot at great speed in the longitudinal direction of the furnace downwards and endeavour vto seek an exit along the shortest path from the combustion chamber behind and below the lowest, rearward point of the grate, so that a flat band of flame is formed which does not come in contact at all with the roof of the combustion chamber and only in slight contact with the sides thereof. Thus, the water-tubes of the roof and sides of the combustion chamber are not licked by the flames, so that the dreaded dirtying of the heating surface and incrustations of clinker, more particularly where coal rich in gas is used, are eo' ipso eliminated, with the result that an invariably constant efficiency of heating of the water-tubes is'assured. In order to still further insure against deposits of clinker of this nature and to compel the flames, so to say, to pass only medially through the tubular combustion chamber, the superheater space 1' or the cross section of the inlet to that space can, for example, be narrower than the furnace. Thus, the width of the furnace chamber can be 4 metres and the width of the down draught or superheater space y only 3 metres. Since the furnace gases invariably choose the shortest path of least resistance and are brought together at the end of the grate to within about I metre,.the adoption of these measures almost entirely eliminates any licking of the upper and lateral water-tubes.

A further means of this kind is hereinafter described and illustrated in Figs. 9 and 10.

A very special advantage of the described arrangement is the possibility afforded of providing observation openings between the watertubes, through which the bed of the furnace, i. e., the grate, as well as the rearward formation of the flame can be observed. A possibility of this kind is, of course, of very great practical value, since it allows of the constant supervision from above of the furnace along its entire length and breadth. The same possibility likewise exists of course in the case of the rear vertical tube wall, such as shown by way of example in Figs. 1 and 3. Here also, and without running any risk, inspection openings can be arranged, such'as marked for example at q and q in Fig. 3, where the inspection opening q is used for the purpose of observing the end of the grate and q for observing the rear ash pit.

It will often be found convenient to arrange further water-tubes inside the tubular furnace chamber along its longitudinal direction. The purpose of these tubes is to increase the quantity of heat absorbed by the water-tubes and thereby to reduce the temperature of the waste gasesat the end of the tubular furnace chamber. It is thus possible to regulate the temperature of the waste gases within wide limits by means of the number and suitable arrangement of these additional tub-es, it being a feature of great importance that the tubes can be arranged in the form of vertical division walls so as to divide the furnace chamber into compartments, as shown for example in Figs. 3 and 4. In this embodiment the automatic stoker grate (mechanical stoker) is again shown at a. It can be cooled or non-cooled. In the embodiment shown, by way of example, it is cooled by means of a special cooling-water circulating system. The cooling can, for course, also be effected by means of the boiler water by the connection of the grate to the boiler, or by any other suitable means. The tubular combustion chamber 1 comprises watertubes which connect the lower drum n-to the upper drum 0. The lower drum can of course be replaced by a rectangular box or other collecting and distributing member. The water is returned from the drum 0 to the drum n, for example, by means of external pipes, or by any other means.

In this embodiment the gases issuing from the combustion chamber 1' flow likewise into a space 11 beneath the combustion chamber and in which they pass along one or more uni or contra-flow superheaters g. The gases then flow, for example, into an air pre-heater w in which the air for combustion is preheated to a high temperature, say 400 to 500 C. The arrangement in this case can be such that the gases leave this air preheater at a temperature of about 250 C., no further use being then made of the waste heat. There is, however, no reason why it should not be utilized, nor why, according to circumstances and as above described, the heat of the gases issuing from the radiation chamber 1 should not be varied as may be desired. For instance, the gases coming from the superheater can also be used for pro-drying brown coal where the latter is used as fuel. For this purpose the gases must be passed along the brown coal in a suitable device, by means of which the use of brown coal as a fuel can be rendered very economical. The furnace chamber, enclosed by water-tubes b is then subdivided cellularly into spaces a, 2 2 e by means of vertical walls 1 which may be likewise constituted of water-tubes. All these walls 1 form additional heating surfaces, and on very cheap lines, seeing that the water-tubes composing the walls 7' are irradiated on both sides. As is obvious herefrom, the extent of the heating surface heated or irradiated by one superficial unit of the grate can be varied within wide limits by inserting as many of these partition walls as may be desired. In the described design of boiler, the ratio, for example, of grate surface to directly irradiated water-tube surface is, due to this novel arrangement, twice as great as it would be if the partition walls 7* were to be omitted.

As shown in Fig. 4, the lowermost tube or tubes 0 of the Walls of tubes 1" can be laid in or below the path of the grate, so that they remain cold and thus render possible the return of the water to the lower drum. Of course, the cross section of these lowermost tubes can be suitably dimensioned in order to ensure an ample return flow of water.

The embodiment of the invention just described due to the possibility aiforded of the adoption of this sub-division, is more particularly suitable for purposes of heating with coal dust, oil or gas burners, one burner being arranged in front of each compartment in the direction, say, of the arrow l2 (see Fig. 3).

In the modification shown in Fig. 5, the walls of the compartments 1" run about half-way up from the grate into the combustion space. In this embodiment, as also everywhere else where the wall of tubes 7' is' brought down on to the grate, a corresponding constriction of the width of the grate, i. e., of the glowing layer, is naturally thereby obtained to the extent of the thickness of the walls of tubes 1', a fact which must be taken into consideration by the designer.

An inverse modification is shown in Fig. 6 in which the division walls 1" extend about half-way down from the roof of the combustion chamber. In this embodiment the lowermost tubes 11 are irradiated directly by the grate and almost throughout their entire area. In this as well as in the other embodiments gaps u can be left in the row of tubes composing the roof of the furnace and lying above the walls of tubes 1, and these gaps can be closed by means of a suitable end brick, or the like. These gaps facilitate the changing of defective boiler tubes.

In Fig. 7 the tubes composing the division walls 7 are spaced fairly far apart, in order to obtain a more tempered exchange of heat.

Finally Fig. 8 show a modification in which simply a number of tubes?" are arranged in a suitable manner, without any special sub-division of the furnace chamber being aimed at.

Figs. 9 and 10 show how, corresponding to Fig. 2, the furnace gases can be constricted with the aid of suitable deflectors t in order that so far as is possible they shall not come in contact with the division walls of tubes and dirty them. This constriction of the furnace gases is effected at the end of the comparted furnace chambers z, 2 e 2 for example with the aid of baiiie plates 1. arranged as shown in Fig. 10. The baffie plates must, of course, be made of some fire-proof material, and if arranged, as shown in the drawings, close to, i. e., above the water-tubes they will reflect on to the water-tubes a considerable portion of the heat absorbed by said baifle plates and thus be cooled to a certain extent. The plates t can, of course, be replaced by water-cooled beams, fire-clay bricks or other means, for example, by the bending of the tubes, all of which serve the same purpose, 1. e., of constricting the cross section of the furnace at the end of the furnace and thereby preventing the furnace gases, which follow the shortest path, from striking directly against the walls of the tubes. The transmission of the heat to the tubes is thus effected merely by radiation, and without this radiation being detrimentally affected by incrustations, or the like. In Fig. 10 the plates 15 are shown pivoted, so that the constriction due to these plates can be regulated more or less by the swinging of the plates toward or away from. the tubular walls according to operating conditions.

Ihe same object as aimed at in the embodiing tubes is thereby afforded.

All the embodiments of the invention as described and illustrated in Figs. 4 to 12 allow of good control of the temperature of the furnace gases at the end of the furnace chamber, either because of the number of longitudinal tubes arranged in the furnace chamber, or by reason of the number and height of the division walls and of the number and spacing apart of the watertubes constituting these division walls.

It is to be understood that dust fired, gas fired, or oil fired furnaces, can be used in the place of grate firing as described, and that the invention include these types of furnaces.

What I claim is:

1. In a water-tube boiler, in combination with an automatic stoker grate, a channel-like furnace chamber of elongated substantially tubular shape formed of water-tubes extending in'the longitudinal direction of the furnace and sloping downwards towards and beyond the rear end of said grate, partition walls in said furnace chamber dividing same into compartments and also formed of Water-tubes, gaps being left above said partitions at certain intervals, so as to make said water-tubes readily accessible.

2. In a water-tube boiler, in combination with a rearwardly sloping automatic stoker grate, a fire-chamber of considerable length relative to its height and formed of elongated water-tubes, those on top being disposed substantially parallel to said grate so as to form therewith an elongated flue-like chamber, the said water-tubes extending beyond the rear edge of said grate where they are bent downwards thereby compelling a'downward flow and complete combustion of the fire gases.

3. In a water-tube boiler, in combination with a rearwardly sloping automatic stoker grate, a

fire-chamber of considerable length relative to its height and formed of elongated water-tubes, those on top being disposed substantially parallel to said grate so as to form therewith an elongated flue-like chamber, the said water-tubes extending beyond the rear edge of said grate where they are bent downwards thereby compelling a downward flow and complete combustion of the fire gases, and means provided at the rear end of said fire chamber restricting the flow of the gases.

4. In a water-tube boiler, in combination with a rearwardly sloping automatic stoker grate, a fire-chamber of considerable length relative to its height and formed of elongated water-tubes, those on top being disposed substantially parallel to said grate so as to form therewith an elongated flue-like chamber, the said water-tubes extending beyond the rear edge or" said grate where they are bent downwards thereby compelling a downward flow and complete combustion of the fire gases, and partitions in said fire chamber formed of longitudinally extending water-tubes and dividing said chamber into separate flue-like compartments.

5. In a water-tube boiler, in combination with the boiler and an automatic stoker grate, a lower drum, a channel-like furnace chamber of elongated substantially tubular shape formed of water tubes connected to said boiler and said drum and extending in the longitudinal direction of said furnace chamber, sloping downwards beyond the rear end of said grate, the sloping portions of the water tubes forming part of the grate being bent apart thus afiording an escape for the clinkers.

FERDINAND GRAAFEN. 

